Simple text landing page

I’m currently developing my next WP website, and since I already purchased the hosting/domain, I want to display a “coming soon” page. I looked for options on theme stores, but none of them suits my needs since all I need is a simple page with some text, a image, a full-color background and a section for people putting their emails to be warned when the site is launched.

I’m sure this is a simple thing to do with my basic knowledge of HTML, but I can’t figure it out. Can someone please help me? Thanks!